Linear stepper actuator ink jet printing mechanism

ABSTRACT

This patent describes an ink jet printer which uses a linear stepper actuator to eject ink from a nozzle chamber. The linear stepper actuator is interconnected to a plunger and actuates the plunger to eject ink. The plunger is sealed in the nozzle chamber and has a hydrophobic surface located alongside at least one wall of a nozzle chamber and the linear actuator is driven in three phases by a series of electromagnets which are duplicated for each driving phase and arranged in opposing pairs.

CROSS REFERENCES TO RELATED APPLICATIONS

The following Australian provisional patent applications are herebyincorporated by cross-reference. For the purposes of location andidentification, U.S. patent applications identified by their U.S. patentapplication serial numbers (USSN) are listed alongside the Australianapplications from which the U.S. patent applications claim the right ofpriority.

U.S. PAT./PATENT APPLI- CROSS-REFERENCED CATION (CLAIMING RIGHTAUSTRALIAN OF PRIORITY FROM PROVISIONAL PATENT AUSTRALIAN PROVI- DOCKETAPPLICATION NO. SIONAL APPLICATION) NO. PO7991 09/113,060 ART01 PO850509/113,070 ART02 PO7988 09/113,073 ART03 PO9395 09/112,748 ART04 PO801709/112,747 ART06 PO8014 09/112,776 ART07 PO8025 09/112,750 ART08 PO803209/112,746 ART09 PO7999 09/112,743 ART10 PO7998 09/112,742 ART11 PO803109/112,741 ART12 PO8030 09/112,740 ART13 PO7997 09/112,739 ART15 PO797909/113,053 ART16 PO8015 09/112,738 ART17 PO7978 09/113,067 ART18 PO798209/113,063 ART19 PO7989 09/113,069 ART20 PO8019 09/112,744 ART21 PO798009/113,058 ART22 PO8018 09/112,777 ART24 PO7938 09/113,224 ART25 PO801609/112,804 ART26 PO8024 09/112,805 ART27 PO7940 09/113,072 ART28 PO793909/112,785 ART29 PO8501 09/112,797 ART30 PO8500 09/112,796 ART31 PO798709/113,071 ART32 PO8022 09/112,824 ART33 PO8497 09/113,090 ART34 PO802009/112,823 ART38 PO8023 09/113,222 ART39 PO8504 09/112,786 ART42 PO800009/113,051 ART43 PO7977 09/112,782 ART44 PO7934 09/113,056 ART45 PO799009/113,059 ART46 PO8499 09/113,091 ART47 PO8502 09/112,753 ART48 PO798109/113,055 ART50 PO7986 09/113,057 ART51 PO7983 09/113,054 ART52 PO802609/112,752 ART53 PO8027 09/112,759 ART54 PO8028 09/112,757 ART56 PO939409/112,758 ART57 PO9396 09/113,107 ART58 PO9397 09/112,829 ART59 PO939809/112,792 ART60 PO9399   6,106,147 ART61 PO9400 09/112,790 ART62 PO940109/112,789 ART63 PO9402 09/112,788 ART64 PO9403 09/112,795 ART65 PO940509/112,749 ART66 PP0959 09/112,784 ART68 PP1397 09/112,783 ART69 PP237009/112,781 DOT01 PP2371 09/113,052 DOT02 PO8003 09/112,834 Fluid01PO8005 09/113,103 Fluid02 PO9404 09/113,101 Fluid03 PO8066 09/112,751IJ01 PO8072 09/112,787 IJ02 PO8040 09/112,802 IJ03 PO8071 09/112,803IJ04 PO8047 09/113,097 IJ05 PO8035 09/113,099 IJ06 PO8044 09/113,084IJ07 PO8063 09/113,066 IJ08 PO8057 09/112,778 IJ09 PO8056 09/112,779IJ10 PO8069 09/113,077 IJ11 PO8049 09/113,061 IJ12 PO8036 09/112,818IJ13 PO8048 09/112,816 IJ14 PO8070 09/112,772 IJ15 PO8067 09/112,819IJ16 PO8001 09/112,815 IJ17 PO8038 09/113,096 IJ18 PO8033 09/113,068IJ19 PO8002 09/113,095 IJ20 PO8068 09/112,808 IJ21 PO8062 09/112,809IJ22 PO8034 09/112,780 IJ23 PO8039 09/113,083 IJ24 PO8041 09/113,121IJ25 PO8004 09/113,122 IJ26 PO8037 09/112,793 IJ27 PO8043 09/112,794IJ28 PO8042 09/113,128 IJ29 PO8064 09/113,127 IJ30 PO9389 09/112,756IJ31 PO9391 09/112,755 IJ32 PP0888 09/112,754 IJ33 PP0891 09/112,811IJ34 PP0890 09/112,812 IJ35 PP0873 09/112,813 IJ36 PP0993 09/112,814IJ37 PP0890 09/112,764 IJ38 PP1398 09/112,765 IJ39 PP2592 09/112,767IJ40 PP2593 09/112,768 IJ41 PP3991 09/112,807 IJ42 PP3987 09/112,806IJ43 PP3985 09/112,820 IJ44 PP3983 09/112,821 IJ45 PO7935 09/112,822IJM01 PO7936 09/112,825 IJM02 PO7937 09/112,826 IJM03 PO8061 09/112,827IJM04 PO8054 09/112,828 IJM05 PO8065   6,071,750 IJM06 PO8055 09/113,108IJM07 PO8053 09/113,109 IJM08 PO8078 09/113,123 IJM09 PO7933 09/113,114IJM10 PO7950 09/113,115 IJM11 PO7949 09/113,129 IJM12 PO8060 09/113,124IJM13 PO8059 09/113,125 IJM14 PO8073 09/113,126 IJM15 PO8076 09/113,119IJM16 PO8075 09/113,120 IJM17 PO8079 09/113,221 IJM18 PO8050 09/113,116IJM19 PO8052 09/113,118 IJM20 PO7948 09/113,117 IJM21 PO7951 09/113,113IJM22 PO8074 09/113,130 IJM23 PO7941 09/113,110 IJM24 PO8077 09/113,112IJM25 PO8058 09/113,087 IJM26 PO8051 09/113,074 IJM27 PO8045   6,110,754IJM28 PO7952 09/113,088 IJM29 PO8046 09/112,771 IJM30 PO9390 09/112,769IJM31 PO9392 09/112,770 IJM32 PP0889 09/112,798 IJM35 PP0887 09/112,801IJM36 PP0882 09/112,800 IJM37 PP0874 09/112,799 IJM38 PP1396 09/113,098IJM39 PP3989 09/112,833 IJM40 PP2591 09/112,832 IJM41 PP3990 09/112,831IJM42 PP3986 09/112,830 IJM43 PP3984 09/112,836 IJM44 PP3982 09/112,835IJM45 PP0895 09/113,102 IR01 PP0870 09/113,106 IR02 PP0869 09/113,105IR04 PP0887 09/113,104 IR05 PP0885 09/112,810 IR06 PP0884 09/112,766IR10 PP0886 09/113,085 IR12 PP0871 09/113,086 IR13 PP0876 09/113,094IR14 PP0877 09/112,760 IR16 PP0878 09/112,773 IR17 PP0879 09/112,774IR18 PP0883 09/112,775 IR19 PP0880   6,152,619 IR20 PP0881 09/113,092IR21 PO8006   6,087,638 MEMS02 PO8007 09/113,093 MEMS03 PO800809/113,062 MEMS04 PO8010   6,041,600 MEMS05 PO8011 09/113,082 MEMS06PO7947   6,067,797 MEMS07 PO7944 09/113,080 MEMS09 PO7946   6,044,646MEMS10 PO9393 09/113,065 MEMS11 PP0875 09/113,078 MEMS12 PP089409/113,075 MEMS13

S

TATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT Notapplicable.

FIELD OF THE INVENTION

The present invention relates to ink jet printing and in particulardiscloses a linear stepper actuator ink jet printer.

The present invention relates to the field of drop on demand ink jetprinting.

BACKGROUND OF THE INVENTION

Many different types of printing have been invented, a large number ofwhich are presently in use. The known forms of print have a variety ofmethods for marking the print media with a relevant marking media.Commonly used forms of printing include offset printing, laser printingand copying devices, dot matrix type impact printers, thermal paperprinters, film recorders, thermal wax printers, dye sublimation printersand ink jet printers both of the drop on demand and continuous flowtype. Each type of printer has its own advantages and problems whenconsidering cost, speed, quality, reliability, simplicity ofconstruction and operation etc.

In recent years, the field of ink jet printing, wherein each individualpixel of ink is derived from one or more ink nozzles has becomeincreasingly popular primarily due to its inexpensive and versatilenature.

Many different techniques on ink jet printing have been invented. For asurvey of the field, reference is made to an article by J Moore,“Non-Impact Printing: Introduction and Historical Perspective”, OutputHard Copy Devices, Editors R Dubeck and S Sherr, pages 207 to 220(1988).

Ink Jet printers themselves come in many different types. The use of acontinuous stream ink in ink jet printing appears to date back to atleast 1929 wherein U.S. Pat. No. 1,941,001 by Hansell discloses a simpleform of continuous stream electro-static ink jet printing.

U.S. Pat. No. 3,596,275 by Sweet also discloses a process of acontinuous ink jet printing including the step wherein the ink jetstream is modulated by a high frequency electro-static field so as tocause drop separation. This technique is still used by severalmanufacturers including Elmjet and Scitex (see also U.S. Pat. No.3,373,437 by Sweet et al)

Piezoelectric ink jet printers are also one form of commonly used inkjet printing device. Piezoelectric systems are disclosed by Kyser et.al. in U.S. Pat. No. 3,946,398 (1970) which uses a diaphragm mode ofoperation, by Zolten in U.S. Pat. No. 3,683,212 (1970) which discloses asqueeze mode of operation of a piezoelectric crystal, Stemme in U.S.Pat. No. 3,747,120 (1972) discloses a bend mode of piezoelectricoperation, Howkins in U.S. Pat. No. 4,459,601 discloses a piezoelectricpush mode actuation of the ink jet stream and Fischbeck in U.S. Pat. No.4,584,590 which discloses a shear mode type of piezoelectric transducerelement.

Recently, thermal ink jet printing has become an extremely popular formof ink jet printing. The ink jet printing techniques include thosedisclosed by Endo et al in GB 2007162 (1979) and Vaught et al in U.S.Pat. No. 4,490,728. Both the aforementioned references disclosed ink jetprinting techniques rely upon the activation of an electrothermalactuator which result in the creation of bubble in a constricted space,such as a nozzle, which thereby causes the ejection of ink from anaperture connected to the confined space onto a relevant print media.Printing devices using the electro-thermal actuator are manufactured bymanufacturers such as Canon and Hewlett Packard.

As can be seen from the foregoing, many different types of printingtechnologies are available. Ideally, a printing technology should have anumber of desirable attributes. These include inexpensive constructionand operation, high speed operation, safe and continuous long termoperation etc. Each technology may have its own advantages anddisadvantages in the areas of cost, speed, quality, reliability, powerusage, simplicity of construction operation, durability and consumables.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide for an alternativeform of ink jet printer which uses a linear stepper actuator to ejectink from a nozzle chamber.

In accordance with a first aspect of the present invention, an ink jetnozzle arrangement is presented comprising: a nozzle chamber having anink ejection port for the ejection of ink, an ink supply reservoir forsupplying ink to the nozzle chamber, a plunger located within the nozzlechamber and further, a linear stepper actuator interconnected to theplunger and adapted to actuate the plunger so as to cause the ejectionof ink from the ink ejection port. At least one surface of the plungerlocated alongside a wall of the nozzle chamber is hydrophobic.Preferably, the linear actuator interconnected to the plunger in the jetnozzle chamber is driven in three phases by a series of electromagnets.Preferably, a series of twelve electromagnets is arranged in opposingpair alongside the linear actuator. Further, each phase is duplicatedresulting in four electromagnets for each phase. The ink jet nozzle hasan open wall along a back surface of the plunger which comprises aseries of posts adapted to form a filter to filter ink flowing throughthe open wall into the nozzle chamber. The linear actuator constructionincludes a guide at the end opposite to the nozzle chamber for guidingthe linear actuator.

BRIEF DESCRIPTION OF THE DRAWINGS

Notwithstanding any other forms which may fall within the scope of thepresent invention, preferred forms of the invention will now bedescribed, by way of example only, with reference to the accompanyingdrawings in which:

FIG. 1 is a cut-out top view of an ink jet nozzle in accordance with thepreferred embodiment;

FIG. 2 is an exploded perspective view illustrating the construction ofa single ink jet nozzle in accordance with the preferred embodiment;

FIG. 3 provides a legend of the materials indicated in FIGS. 4 to 24;and

FIGS. 4 to FIG. 24 illustrate sectional views of the manufacturing stepsin one form of construction of an ink jet printhead nozzle.

DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS

In the preferred embodiment, a linear stepper motor is utilised tocontrol a plunger device. The plunger device compressing ink within anozzle chamber so as to thereby cause the ejection of ink from thechamber on demand.

Turning to FIG. 1, there is illustrated a single nozzle arrangement 10as constructed in accordance with the preferred embodiment. The nozzlearrangement 10 includes a nozzle chamber 11 into which ink flows via anozzle chamber filter portion 14 which includes a series of posts whichfilter out foreign bodies in the ink in flow. The nozzle chamber 11includes an ink ejection port 15 for the ejection of ink on demand.Normally, the nozzle chamber 11 is filled with ink.

A linear actuator 16 is provided for rapidly compressing a nickelferrous plunger 18 into the nozzle chamber 11 so as to compress thevolume of ink within chamber 11 to thereby cause ejection of drops fromthe ink ejection port 15. The plunger 18 is connected to the steppermoving pole device 16 which is actuated by means of a three phasearrangement of electromagnets 20 to 31. The electromagnets are driven inthree phases with electro magnets 20, 26, 23 and 29 being driven in afirst phase, electromagnets 21, 27, 24, 30 being driven in a secondphase and electromagnets 22, 28, 25, 31 being driven in a third phase.The electromagnets are driven in a reversible manner so as to de-actuateplunger 18 via actuator 16. The actuator 16 is guided at one end by ameans of guide 33, 34. At the other end, the plunger 18 is coated with ahydrophobic material such as polytetrafluoroethylene (PTFE) which canform a major part of the plunger 18. The PTFE acts to repel the ink fromthe nozzle chamber 11 resulting in the creation of a membrane eg. 38, 39between the plunger 18 and side walls eg. 36, 37. The surface tensioncharacteristics of the membranes 38, 39 act to balanced one anotherthereby guiding the plunger 18 within the nozzle chamber. The meniscuseg. 38, 39 further stops ink from flowing out of the chamber 11 andhence the electromagnets 20 to 31 can be operated in normal air.

The nozzle arrangement 10 is therefore operated to eject drops on demandby means of activating the actuator 16 by appropriately synchroniseddriving of electromagnets 20 to 31. The actuation of the actuator 16results in the plunger 18 moving towards the nozzle ink ejection port 15thereby causing ink to be ejected from the port 15.

Subsequently, the electromagnets are driven in reverse thereby movingthe plunger in an opposite direction resulting in the in flow of inkfrom an ink supply connected to the ink inlet port 14.

Preferably, multiple ink nozzle arrangements 10 can be constructedadjacent to one another to form a multiple nozzle ink ejectionmechanism. The nozzle arrangements 10 are preferably constructed in anarray print head constructed on a single silicon wafer which issubsequently diced in accordance with requirements. The diced printheads can then be interconnected to an ink supply which can comprise athrough chip ink flow or ink flow from the side of a chip.

Turning now to FIG. 2, there is shown an exploded perspective of thevarious layers of the nozzle arrangement 10. The nozzle arrangement canbe constructed on top of a silicon wafer 40 which has a standardelectronic circuitry layer such as a two level metal CMOS layer 41. Thetwo metal CMOS provides the drive and control circuitry for the ejectionof ink from the nozzles by interconnection of the electromagnets to theCMOS layer. On top of the CMOS layer 41 is a nitride passivation layer42 which passivates the lower layers against any ink erosion in additionto any etching of the lower CMOS glass layer should a sacrificialetching process be used in the construction of the nozzle arrangement10.

On top of the nitride layer 42 is constructed various other layers. Thewafer layer 40, the CMOS layer 41 and the nitride passivation layer 42are constructed with the appropriate fires for interconnecting to theabove layers. On top of the nitride layer 42 is constructed a bottomcopper layer 43 which interconnects with the CMOS layer 41 asappropriate. Next, a nickel ferrous layer 45 is constructed whichincludes portions for the core of the electromagnets and the actuator 16and guides 31, 32. On top of the NiFe layer 45 is constructed a secondcopper layer 46 which forms the rest of the electromagnetic device. Thecopper layer 46 can be constructed using a dual damascene process. Nexta PTFE layer 47 is laid down followed by a nitride layer 48 whichincludes the side filter portions and side wall portions of the nozzlechamber. In the top of the nitride layer 48, the ejection port 15 andthe rim 51 are constructed by means of etching. In the top of thenitride layer 48 is also provided a number of apertures 50 which areprovided for the sacrificial etching of any sacrificial material used inthe construction of the various lower layers including the nitride layer48.

It will be understood by those skilled in the art of construction ofmicro-electro-mechanical systems (MEMS) that the various layers 43, 45to 48 can be constructed by means of utilising a sacrificial material todeposit the structure of various layers and subsequent etching away ofthe sacrificial material as to release the structure of the nozzlearrangement 10.

For a general introduction to a micro-electro mechanical system (MEMS)reference is made to standard proceedings in this field including theproceedings of the SPIE (International Society for Optical Engineering),volumes 2642 and 2882 which contain the proceedings for recent advancesand conferences in this field.

One form of detailed manufacturing process which can be used tofabricate monolithic ink jet print heads operating in accordance withthe principles taught by the present embodiment can proceed utilizingthe following steps:

1. Using a double sided polished wafer 40, complete drive transistors,data distribution, and timing circuits using a 0.5 micron, one poly, 2metal CMOS process. This step is shown in FIG. 4. For clarity, thesediagrams may not be to scale, and may not represent a cross sectionthough any single plane of the nozzle. FIG. 3 is a key torepresentations of various materials in these manufacturing diagrams,and those of other cross referenced ink jet configurations.

2. Deposit 1 micron of sacrificial material 60.

3. Etch the sacrificial material and the CMOS oxide layers down tosecond level metal using Mask 1. This mask defines the contact vias 61from the second level metal electrodes to the solenoids. This step isshown in FIG. 5.

4. Deposit a barrier layer of titanium nitride (TiN) and a seed layer ofcopper.

5. Spin on 2 microns of resist 62, expose with Mask 2, and develop. Thismask defines the lower side of the solenoid square helix. The resistacts as an electroplating mold. This step is shown in FIG. 6.

6. Electroplate 1 micron of copper 63. Copper is used for its lowresistivity (which results in higher efficiency) and its highelectromigration resistance, which increases reliability at high currentdensities.

7. Strip the resist and etch the exposed barrier and seed layers. Thisstep is shown in FIG. 7.

8. Deposit 0.1 microns of silicon nitride.

9. Deposit a seed layer of cobalt nickel iron alloy. CoNiFe is chosendue to a high saturation flux density of 2 Tesla, and a low coercivity.[Osaka, Tetsuya et al, A soft magnetic CoNiFe film with high saturationmagnetic flux density, Nature 392, 796-798 (1998)].

10. Spin on 3 microns of resist 64, expose with Mask 3, and develop.This mask defines all of the soft magnetic parts, being the fixedmagnetic pole of the solenoids, the moving poles of the linear actuator,the horizontal guides, and the core of the ink plunger. The resist actsas an electroplating mold. This step is shown in FIG. 8.

11. Electroplate 2 microns of CoNiFe 65. This step is shown in FIG. 9.

12. Strip the resist and etch the exposed seed layer. This step is shownin FIG. 10.

13. Deposit 0.1 microns of silicon nitride (Si3N4) (not shown).

14. Spin on 2 microns of resist 66, expose with Mask 4, and develop.This mask defines the solenoid vertical wire segments 67, for which theresist acts as an electroplating mold. This step is shown in FIG. 11.

15. Etch the nitride down to copper using the Mask 4 resist.

16. Electroplate 2 microns of copper 68. This step is shown in FIG. 12.

17. Deposit a seed layer of copper.

18. Spin on 2 microns of resist 70, expose with Mask 5, and develop.This mask defines the upper side of the solenoid square helix. Theresist acts as an electroplating mold. This step is shown in FIG. 13.

19. Electroplate 1 micron of copper 71. This step is shown in FIG. 14.

20. Strip the resist and etch the exposed copper seed layer, and stripthe newly exposed resist. This step is shown in FIG. 15.

21. Open the bond pads using Mask 6.

22. Wafer probe. All electrical connections are complete at this point,bond pads are accessible, and the chips are not yet separated.

23. Deposit 5 microns of PTFE 72.

24. Etch the PTFE down to the sacrificial layer using Mask 7. This maskdefines the ink plunger. This step is shown in FIG. 16.

25. Deposit 8 microns of sacrificial material 73. Planarize using CMP tothe top of the PTFE ink pusher. This step is shown in FIG. 17.

26. Deposit 0.5 microns of sacrificial material 75. This step is shownin FIG. 18.

27. Etch all layers of sacrificial material using Mask 8. This maskdefines the nozzle chamber wall 36. This step is shown in FIG. 19.

28. Deposit 3 microns of PECVD glass 76.

29. Etch to a depth of (approx.) 1 micron using Mask 9. This maskdefines the nozzle rim 51. This step is shown in FIG. 20.

30. Etch down to the sacrificial layer using Mask 10. This mask definesthe roof of the nozzle chamber, the nozzle 15, and the sacrificial etchaccess holes 50. This step is shown in FIG. 21.

31. Back-etch completely through the silicon wafer (with, for example,an ASE Advanced Silicon Etcher from Surface Technology Systems) usingMask 11. Continue the back-etch through the CMOS glass layers until thesacrificial layer is reached. This mask defines the ink inlets 80 whichare etched through the wafer. The wafer is also diced by this etch. Thisstep is shown in FIG. 22.

32. Etch the sacrificial material. The nozzle chambers are cleared, theactuators freed, and the chips are separated by this etch. This step isshown in FIG. 23.

33. Mount the printheads in their packaging, which may be a moldedplastic former incorporating ink channels which supply the appropriatecolor ink to the ink inlets at the back of the wafer. The package alsoincludes a piezoelectric actuator attached to the rear of the inkchannels. The piezoelectric actuator provides the oscillating inkpressure required for the ink jet operation.

34. Connect the printheads to their interconnect systems. For a lowprofile connection with minimum disruption of airflow, TAB may be used.Wire bonding may also be used if the printer is to be operated withsufficient clearance to the paper.

35. Hydrophobize the front surface of the printheads.

36. Fill the completed printheads with ink 81 and test them. A fillednozzle is shown in FIG. 24.

Further, it would be readily understood that various other forms ofconstruction, including substitution of various materials for othersuitable materials and variations in the utilisation of nitridepassivation layers will be readily evident to those skilled in the artwith the preferred embodiment providing a merely illustrative example ofthe present invention.

It would be appreciated by a person skilled in the art that numerousvariations and/or modifications may be made to the present invention asshown in the specific embodiment without departing from the spirit orscope of the invention as broadly described. The present embodiment is,therefore, to be considered in all respects to be illustrative and notrestrictive.

The presently disclosed ink jet printing technology is potentiallysuited to a wide range of printing systems including: color andmonochrome office printers, short run digital printers, high speeddigital printers, offset press supplemental printers, low cost scanningprinters, high speed pagewidth printers, notebook computers with inbuiltpagewidth printers, portable color and monochrome printers, color andmonochrome copiers, color and monochrome facsimile machines, combinedprinter, facsimile and copying machines, label printers, large formatplotters, photograph copiers, printers for digital photographic‘minilabs’, video printers, PHOTO CD (PHOTO CD is a trademark used bythe Eastman Kodak Company) printers, portable printers for PDAs,wallpaper printers, indoor sign printers, billboard printers, fabricprinters, camera printers and fault tolerant commercial printer arrays.

Ink Jet Technologies

The embodiments of the invention use an ink jet printer type device. Ofcourse many different devices could be used. However presently popularink jet printing technologies are unlikely to be suitable.

The most significant problem with thermal ink jet is power consumption.This is approximately 100 times that required for high speed, and stemsfrom the energy-inefficient means of drop ejection. This involves therapid boiling of water to produce a vapor bubble which expels the ink.Water has a very high heat capacity, and must be superheated in thermalink jet applications. This leads to an efficiency of around 0.02%, fromelectricity input to drop momentum (and increased surface area) out.

The most significant problem with piezoelectric ink jet is size andcost. Piezoelectric crystals have a very small deflection at reasonabledrive voltages, and therefore require a large area for each nozzle.Also, each piezoelectric actuator must be connected to its drive circuiton a separate substrate. This is not a significant problem at thecurrent limit of around 300 nozzles per printhead, but is a majorimpediment to the fabrication of pagewidth printheads with 19,200nozzles.

Ideally, the ink jet technologies used meet the stringent requirementsof in-camera digital color printing and other high quality, high speed,low cost printing applications. To meet the requirements of digitalphotography, new ink jet technologies have been created. The targetfeatures include:

low power (less than 10 Watts)

high resolution capability (1,600 dpi or more)

photographic quality output

low manufacturing cost

small size (pagewidth times minimum cross section)

high speed (<2 seconds per page).

All of these features can be met or exceeded by the ink jet systemsdescribed below with differing levels of difficulty. Forty-fivedifferent ink jet technologies have been developed by the Assignee togive a wide range of choices for high volume manufacture. Thesetechnologies form part of separate applications assigned to the presentAssignee as set out in the table under the heading Cross References toRelated Applications.

The ink jet designs shown here are suitable for a wide range of digitalprinting systems, from battery powered one-time use digital cameras,through to desktop and network printers, and through to commercialprinting systems.

For ease of manufacture using standard process equipment, the printheadis designed to be a monolithic 0.5 micron CMOS chip with MEMS postprocessing. For color photographic applications, the printhead is 100 mmlong, with a width which depends upon the ink jet type. The smallestprinthead designed is IJ38, which is 0.35 mm wide, giving a chip area of35 square mm. The printheads each contain 19,200 nozzles plus data andcontrol circuitry.

Ink is supplied to the back of the printhead by injection molded plasticink channels. The molding requires 50 micron features, which can becreated using a lithographically micromachined insert in a standardinjection molding tool. Ink flows through holes etched through the waferto the nozzle chambers fabricated on the front surface of the wafer. Theprinthead is connected to the camera circuitry by tape automatedbonding.

Tables of Drop-on-Demand Ink Jets

The present invention is useful in the field of digital printing, inparticular, ink jet printing.

Eleven important characteristics of the fundamental operation ofindividual ink jet nozzles have been identified. These characteristicsare largely orthogonal, and so can be elucidated as an elevendimensional matrix. Most of the eleven axes of this matrix includeentries developed by the present assignee.

The following tables form the axes of an eleven dimensional table of inkjet types.

Actuator mechanism (18 types)

Basic operation mode (7 types)

Auxiliary mechanism (8 types)

Actuator amplification or modification method (17 types)

Actuator motion (19 types)

Nozzle refill method (4 types)

Method of restricting back-flow through inlet (10 types)

Nozzle clearing method (9 types)

Nozzle plate construction (9 types)

Drop ejection direction (5 types)

Ink type (7 types)

The complete eleven dimensional table represented by these axes contains36.9 billion possible configurations of ink jet nozzle. While not all ofthe possible combinations result in a viable ink jet technology, manymillion configurations are viable. It is clearly impractical toelucidate all of the possible configurations. Instead, certain ink jettypes have been investigated in detail. These are designated IJ01 toIJ45 which match the docket numbers in the table under the heading CrossReferences to Related Applications.

Other ink jet configurations can readily be derived from these 45examples by substituting alternative configurations along one or more ofthe 11 axes. Most of the IJ01 to IJ45 examples can be made into ink jetprintheads with characteristics superior to any currently available inkjet technology.

Where there are prior art examples known to the inventor, one or more ofthese examples are listed in the examples column of the tables below.The IJ01 to IJ45 series are also listed in the examples column. In somecases, a print technology may be listed more than once in a table, whereit shares characteristics with more than one entry.

Suitable applications for the ink jet technologies include: Homeprinters, Office network printers, Short run digital printers,Commercial print systems, Fabric printers, Pocket printers, Internet WWWprinters, Video printers, Medical imaging, Wide format printers,Notebook PC printers, Fax machines, Industrial printing systems,Photocopiers, Photographic minilabs etc.

The information associated with the aforementioned 11 dimensional matrixare set out in the following tables.

ACTUATOR MECHANISM (APPLIED ONLY TO SELECTED INK DROPS) DescriptionAdvantages Disadvantages Examples Thermal An electrothermal Large forceHigh power Canon Bubblejet bubble heater heats the ink to generated Inkcarrier 1979 Endo et al GB above boiling point, Simple limited to waterpatent 2,007, 162 transferring significant construction Low efficiencyXerox heater-in-pit heat to the aqueous No moving parts High 1990Hawkins et al ink. A bubble Fast operation temperatures U.S. Pat. No.nucleates and quickly Small chip area required 4,899,181 forms,expelling the required for actuator High mechanical Hewlett-Packard ink.stress TIJ 1982 Vaught et The efficiency of the Unusual al U.S. Pat. No.process is low, with materials required 4,490,728 typically less thanLarge drive 0.05% of the electrical transistors energy being Cavitationcauses transformed into actuator failure kinetic energy of the Kogationreduces drop. bubble formation Large print heads are difficult tofabricate Piezo- A piezoelectric crystal Low power Very large area Kyseret al U.S. Pat. electric such as lead consumption required for actuatorNo. 3,946,398 lanthanum zirconate Many ink types Difficult to ZoltanU.S. Pat. No. (PZT) is electrically can be used integrate with 3,683,212activated, and either Fast operation electronics 1973 Stemme U.S.expands, shears, or High efficiency High voltage Pat. No. 3,747,120bends to apply drive transistors Epson Stylus pressure to the ink,required Tektronix ejecting drops. Full pagewidth IJ04 print headsimpractical due to actuator size Requires electrical poling in highfield strengths during manufacture Electro- An electric field is Lowpower Low maximum Seiko Epson, strictive used to activate consumptionstrain (approx. Usui et all JP electrostriction in Many ink types 0.01%)253401/96 relaxor materials such can be used Large area IJ04 as leadlanthanum Low thermal required for actuator zirconate titanate expansiondue to low strain (PLZT) or lead Electric field Response speed magnesiumniobate strength required is marginal (PMN). (approx. 3.5 V/μm) (˜10 μs)can be generated High voltage without difficulty drive transistors Doesnot require required electrical poling Full pagewidth print headsimpractical due to actuator size Ferro- An electric field is Low powerDifficult to IJ04 electric used to induce a phase consumption integratewith transition between the Many ink types electronics antiferroelectric(AFE) can be used Unusual and ferroelectric (FE) Fast operationmaterials such as phase. Perovskite (<1 μs) PLZSnT are materials such astin Relatively high required modified lead longitudinal strain Actuatorsrequire lanthanum zirconate High efficiency a large area titanate(PLZSnT) Electric field exhibit large strains of strength of around 3 upto 1% associated V/μm can be readily with the AFE to FE provided phasetransition. Electro- Conductive plates are Low power Difficult to IJ02,IJ04 static plates separated by a consumption operate electrostaticcompressible or fluid Many ink types devices in an dielectric (usuallyair). can be used aqueous Upon application of a Fast operationenvironment voltage, the plates The electrostatic attract each other andactuator will displace ink, causing normally need to be drop ejection.The separated from the conductive plates may ink be in a comb or Verylarge area honeycomb structure, required to achieve or stacked toincrease high forces the surface area and High voltage therefore theforce. drive transistors may be required Full pagewidth print heads arenot competitive due to actuator size Electro- A strong electric fieldLow current High voltage 1989 Saito et al, U.S. static pull is appliedto the ink, consumption required Pat. No. 4,799,068 on ink whereupon Lowtemperature May be damaged 1989 Miura et al, electrostatic attraction bysparks due to air U.S. Pat. No. accelerates the ink breakdown 4,810,954towards the print Required field Tone-jet medium. strength increases asthe drop size decreases High voltage drive transistors requiredElectrostatic field attracts dust Permanent An electromagnet Low powerComplex IJ07, IJ10 magnet directly attracts a consumption fabricationelectro- permanent magnet, Many ink types Permanent magnetic displacingink and can be used magnetic material causing drop ejection. Fastoperation such as Neodymium Rare earth magnets High efficiency IronBoron (NdFeB) with a field strength Easy extension required. around 1Tesla can be from single nozzles High local used. Examples are: topagewidth print currents required Samarium Cobalt heads Copper (SaCo)and magnetic metalization should materials in the be used for longneodymium iron boron electromigration family (NdFeB, lifetime and lowNdDyFeBNb, resistivity NdDyFeB, etc) Pigmented inks are usuallyinfeasible Operating temperature limited to the Curie temperature(around 540 K) Soft A solenoid induced a Low power Complex IJ01, IJ05,IJ08, magnetic magnetic field in a soft consumption fabrication IJ10,IJ12, IJ14, core electro- magnetic core or yoke Many ink types Materialsnot IJ15, IJ17 magnetic fabricated from a can be used usually present ina ferrous material such Fast operation CMOS fab such as as electroplatediron High efficiency NiFe, CoNiFe, or alloys such as CoNiFe Easyextension CoFe are required [1], CoFe, or NiFe from single nozzles Highlocal alloys. Typically, the to pagewidth print currents required softmagnetic material heads Copper is in two parts, which metalizationshould are normally held be used for long apart by a spring.electromigration When the solenoid is lifetime and low actuated, the twoparts resistivity attract, displacing the Electroplating is ink.required High saturation flux density is required (2.0-2.1 T isachievable with CoNiFe [1]) Lorenz The Lorenz force Low power Force actsas a IJ06, IJ11, IJ13, force acting on a current consumption twistingmotion IJ16 carrying wire in a Many ink types Typically, only a magneticfield is can be used quarter of the utilized. Fast operation solenoidlength This allows the High efficiency provides force in a magneticfield to be Easy extension useful direction supplied externally to fromsingle nozzles High local the print head, for to pagewidth printcurrents required example with rare heads Copper earth permanentmetalization should magnets. be used for long Only the currentelectromigration carrying wire need be lifetime and low fabricated onthe print- resistivity head, simplifying Pigmented inks materials areusually requirements. infeasible Magneto- The actuator uses the Many inktypes Force acts as a Fischenbeck, striction giant magnetostrictive canbe used twisting motion U.S. Pat. No. effect of materials Fast operationUnusual 4,032,929 such as Terfenol-D (an Easy extension materials suchas IJ25 alloy of terbium, from single nozzles Terfenol-D are dysprosiumand iron to pagewidth print required developed at the Naval heads Highlocal Ordnance Laboratory, High force is currents required henceTer-Fe-NOL). available Copper For best efficiency, the metalizationshould actuator should be pre- be used for long stressed to approx. 8electromigration MPa. lifetime and low resistivity Pre-stressing may berequired Surface Ink under positive Low power Requires Silverbrook, EPtension pressure is held in a consumption supplementary force 0771 658A2 and reduction nozzle by surface Simple to effect drop related patenttension. The surface construction separation applications tension of theink is No unusual Requires special reduced below the materials requiredin ink surfactants bubble threshold, fabrication Speed may be causingthe ink to High efficiency limited by surfactant egress from the Easyextension properties nozzle. from single nozzles to pagewidth printheads Viscosity The ink viscosity is Simple Requires Silverbrook, EPreduction locally reduced to construction supplementary force 0771 658A2 and select which drops are No unusual to effect drop related patentto be ejected. A materials required in separation applications viscosityreduction can fabrication Requires special be achieved Easy extensionink viscosity electrothermally with from single nozzles properties mostinks, but special to pagewidth print High speed is inks can beengineered heads difficult to achieve for a 100:1 viscosity Requiresreduction. oscillating ink pressure A high temperature difference(typically 80 degrees) is required Acoustic An acoustic wave is Canoperate Complex drive 1993 Hadimioglu generated and without a nozzlecircuitry et al, EUP 550,192 focused upon the plate Complex 1993 Elrodet al, drop ejection region. fabrication EUP 572,220 Low efficiency Poorcontrol of drop position Poor control of drop volume Thermo- An actuatorwhich Low power Efficient aqueous IJ03, IJ09, IJ17, elastic bend reliesupon differential consumption operation requires a IJ18, IJ19, IJ20,actuator thermal expansion Many ink types thermal insulator on IJ21,IJ22, IJ23, upon Joule heating is can be used the hot side IJ24, IJ27,IJ28, used. Simple planar Corrosion IJ29, IJ30, IJ31, fabricationprevention can be IJ32, IJ33, IJ34, Small chip area difficult IJ35,IJ36, IJ37, required for each Pigmented inks IJ38 ,IJ39, IJ40, actuatormay be infeasible, IJ41 Fast operation as pigment particles Highefficiency may jam the bend CMOS actuator compatible voltages andcurrents Standard MEMS processes can be used Easy extension from singlenozzles to pagewidth print heads High CTE A material with a very Highforce can Requires special IJ09, IJ17, IJ18, thermo- high coefficient ofbe generated material (e.g. PTFE) IJ20, IJ21, IJ22, elastic thermalexpansion Three methods of Requires a PTFE IJ23, IJ24, IJ27, actuator(CTE) such as PTFE deposition are deposition process, IJ28, IJ29, IJ30,polytetrafluoroethylene under development: which is not yet IJ31, IJ42,IJ43, (PTFE) is used. As chemical vapor standard in ULSI IJ44 high CTEmaterials deposition (CVD), fabs are usually non- spin coating, and PTFEdeposition conductive, a heater evaporation cannot be followedfabricated from a PTFE is a with high conductive material is candidatefor low temperature (above incorporated. A 50 μm dielectric constant350° C.) processing long PTFE bend insulation in ULSI Pigmented inksactuator with Very low power may be infeasible, polysilicon heater andconsumption as pigment particles 15 mW power input Many ink types mayjam the bend can provide 180 μN can be used actuator force and 10 μmSimple planar deflection. Actuator fabrication motions include: Smallchip area Bend required for each Push actuator Buckle Fast operationRotate High efficiency CMOS compatible voltages and currents Easyextension from single nozzles to pagewidth print heads Conduct-ive Apolymer with a high High force can Requires special IJ24 polymercoefficient of thermal be generated materials thermo- expansion (such asVery low power development (High elastic PTFE) is doped with consumptionCTE conductive actuator conducting substances Many ink types polymer) toincrease its can be used Requires a PTFE conductivity to about 3 Simpleplanar deposition process, orders of magnitude fabrication which is notyet below that of copper. Small chip area standard in ULSI Theconducting required for each fabs polymer expands actuator PTFEdeposition when resistively Fast operation cannot be followed heated.High efficiency with high Examples of CMOS temperature (above conductingdopants compatible voltages 350° C.) processing include: and currentsEvaporation and Carbon nanotubes Easy extension CVD deposition Metalfibers from single nozzles techniques cannot Conductive polymers topagewidth print be used such as doped heads Pigmented inks polythiophenemay be infeasible, Carbon granules as pigment particles may jam the bendactuator Shape A shape memory alloy High force is Fatigue limits IJ26memory such as TiNi (also available (stresses maximum number alloy knownas Nitinol - of hundreds of MPa) of cycles Nickel Titanium alloy Largestrain is Low strain (1%) developed at the Naval available (more than isrequired to extend Ordnance Laboratory) 3%) fatigue resistance isthermally switched High corrosion Cycle rate between its weak resistancelimited by heat martensitic state and Simple removal its high stiffnessconstruction Requires unusual austenic state. The Easy extensionmaterials (TiNi) shape of the actuator from single nozzles The latentheat of in its martensitic state to pagewidth print transformation mustis deformed relative to heads be provided the austenic shape. Lowvoltage High current The shape change operation operation causesejection of a Requires pre- drop. stressing to distort the martensiticstate Linear Linear magnetic Linear Magnetic Requires unusual IJ12Magnetic actuators include the actuators can be semiconductor ActuatorLinear Induction constructed with materials such as Actuator (LIA),Linear high thrust, long soft magnetic alloys Permanent Magnet travel,and high (e.g. CoNiFe) Synchronous Actuator efficiency using Somevarieties (LPMSA), Linear planar also require Reluctance semiconductorpermanent magnetic Synchronous Actuator fabrication materials such as(LRSA), Linear techniques Neodymium iron Switched Reluctance Longactuator boron (NdFeB) Actuator (LSRA), and travel is available Requiresthe Linear Stepper Medium force is complex multi- Actuator (LSA).available phase drive circuitry Low voltage High current operationoperation

BASIC OPERATION MODE Description Advantages Disadvantages ExamplesActuator This is the simplest Simple operation Drop repetition Thermalink jet directly mode of operation: the No external rate is usuallyPiezoelectric ink pushes ink actuator directly fields required limitedto around 10 jet supplies sufficient Satellite drops kHz. However, thisIJ01, IJ02, IJ03, kinetic energy to expel can be avoided if is notfundamental IJ04, IJ05, IJ06, the drop. The drop drop velocity is lessto the method, but is IJ07, IJ09, IJ11, must have a sufficient than 4m/s related to the refill IJ12, IJ14, IJ16, velocity to overcome Can beefficient, method normally IJ20, IJ22, IJ23, the surface tension.depending upon the used IJ24, IJ25, IJ26, actuator used All of the dropIJ27, IJ28, IJ29, kinetic energy must IJ30, IJ31, IJ32, be provided bythe IJ33, IJ34, IJ35, actuator IJ36, IJ37, IJ38, Satellite drops IJ39,IJ40, IJ41, usually form if drop IJ42, IJ43, IJ44 velocity is greaterthan 4.5 m/s Proximity The drops to be Very simple print Requires closeSilverbrook, EP printed are selected by head fabrication can proximitybetween 0771 658 A2 and some manner (e.g. be used the print head andrelated patent thermally induced The drop the print media orapplications surface tension selection means transfer roller reductionof does not need to May require two pressurized ink). provide the energyprint heads printing Selected drops are required to separate alternaterows of the separated from the ink the drop from the image in the nozzleby nozzle Monolithic color contact with the print print heads are mediumor a transfer difficult roller. Electro- The drops to be Very simpleprint Requires very Silverbrook, EP static pull printed are selected byhead fabrication can high electrostatic 0771 658 A2 and on ink somemanner (e.g. be used field related patent thermally induced The dropElectrostatic field applications surface tension selection means forsmall nozzle Tone-Jet reduction of does not need to sizes is above airpressurized ink). provide the energy breakdown Selected drops arerequired to separate Electrostatic field separated from the ink the dropfrom the may attract dust in the nozzle by a nozzle strong electricfield. Magnetic The drops to be Very simple print Requires Silverbrook,EP pull on ink printed are selected by head fabrication can magnetic ink0771 658 A2 and some manner (e.g. be used Ink colors other relatedpatent thermally induced The drop than black are applications surfacetension selection means difficult reduction of does not need to Requiresvery pressurized ink). provide the energy high magnetic fields Selecteddrops are required to separate separated from the ink the drop from thein the nozzle by a nozzle strong magnetic field acting on the magneticink. Shutter The actuator moves a High speed (>50 Moving parts are IJ13,IJ17, IJ21 shutter to block ink kHz) operation can required flow to thenozzle. The be achieved due to Requires ink ink pressure is pulsedreduced refill time pressure modulator at a multiple of the Drop timingcan Friction and wear drop ejection be very accurate must be consideredfrequency. The actuator Stiction is energy can be very possible lowShuttered The actuator moves a Actuators with Moving parts are IJ08,IJ15, IJ18, grill shutter to block ink small travel can be required IJ19flow through a grill to used Requires ink the nozzle. The shutterActuators with pressure modulator movement need only small force can beFriction and wear be equal to the width used must be considered of thegrill holes. High speed (>50 Stiction is kHz) operation can possible beachieved Pulsed A pulsed magnetic Extremely low Requires an IJ10magnetic field attracts an ‘ink energy operation is external pulsed pullon ink pusher’ at the drop possible magnetic field pusher ejectionfrequency. An No heat Requires special actuator controls a dissipationmaterials for both catch, which prevents problems the actuator and thethe ink pusher from ink pusher moving when a drop is Complex not to beejected. construction

AUXILIARY MECHANISM (APPLIED TO ALL NOZZLES) Description AdvantagesDisadvantages Examples None The actuator directly Simplicity of Dropejection Most ink jets, fires the ink drop, and construction energy mustbe including there is no external Simplicity of supplied bypiezoelectric and field or other operation individual nozzle thermalbubble. mechanism required. Small physical actuator IJ01, IJ02, IJ03,size IJ04, IJ05, IJ07, IJ09, IJ11, IJ12, IJ14, IJ20, IJ22, IJ23, IJ24,IJ25, IJ26, IJ27, IJ28, IJ29, IJ30, IJ31, IJ32, IJ33, IJ34, IJ35, IJ36,IJ37, IJ38, IJ39, IJ40, IJ41, IJ42, IJ43, IJ44 Oscillating The inkpressure Oscillating ink Requires external Silverbrook, EP ink pressureoscillates, providing pressure can provide ink pressure 0771 658 A2 and(including much of the drop a refill pulse, oscillator related patentacoustic ejection energy. The allowing higher Ink pressure applicationsstimu- actuator selects which operating speed phase and amplitude IJ08,IJ13, IJ15, lation) drops are to be fired The actuators must becarefully IJ17, IJ18, IJ19, by selectively may operate with controlledIJ21 blocking or enabling much lower energy Acoustic nozzles. The inkAcoustic lenses reflections in the ink pressure oscillation can be usedto focus chamber must be may be achieved by the sound on the designedfor vibrating the print nozzles head, or preferably by an actuator inthe ink supply. Media The print head is Low power Precision Silverbrook,EP proximity placed in close High accuracy assembly required 0771 658 A2and proximity to the print Simple print head Paper fibers may relatedpatent medium. Selected construction cause problems applications dropsprotrude from Cannot print on the print head further rough substratesthan unselected drops, and contact the print medium. The drop soaks intothe medium fast enough to cause drop separation. Transfer Drops areprinted to a High accuracy Bulky Silverbrook, EP roller transfer rollerinstead Wide range of Expensive 0771 658 A2 and of straight to the printprint substrates can Complex related patent medium. A transfer be usedconstruction applications roller can also be used Ink can be driedTektronix hot for proximity drop on the transfer roller meltpiezoelectric separation. ink jet Any of the IJ series Electro- Anelectric field is Low power Field strength Silverbrook, EP static usedto accelerate Simple print head required for 0771 658 A2 and selecteddrops towards construction separation of small related patent the printmedium drops is near or applications above air Tone-Jet breakdown DirectA magnetic field is Low power Requires Silverbrook, EP magnetic used toaccelerate Simple print head magnetic ink 0771 658 A2 and field selecteddrops of construction Requires strong related patent magnetic inktowards magnetic field applications the print medium. Cross The printhead is Does not require Requires external IJ06, IJ16 magnetic placed ina constant magnetic materials magnet field magnetic field. The to beintegrated in Current densities Lorenz force in a the print head may behigh, current carrying wire manufacturing resulting in is used to movethe process electromigration actuator problems Pulsed A pulsed magneticVery low power Complex print IJ10 magnetic field is used to operation ispossible head construction field cyclically attract a Small print headMagnetic paddle, which pushes size materials required in on the ink. Asmall print head actuator moves a catch, which selectively prevents thepaddle from moving.

ACTUATOR AMPLIFICATION OR MODIFICATION METHOD Description AdvantagesDisadvantages Examples None No actuator Operational Many actuatorThermal Bubble mechanical simplicity mechanisms have Ink jetamplification is used. insufficient travel, IJ01, IJ02, IJ06, Theactuator directly or insufficient force, IJ07, IJ16, IJ25, drives thedrop to efficiently drive IJ26 ejection process. the drop ejectionprocess Differential An actuator material Provides greater High stressesare Piezoelectric expansion expands more on one travel in a reducedinvolved IJ03, IJ09, IJ17, bend side than on the other. print head areaCare must be IJ18, IJ19, IJ20, actuator The expansion may be taken thatthe IJ21, IJ22, IJ23, thermal, piezoelectric, materials do not IJ24,IJ27, IJ29, magnetostrictive, or delaminate IJ30, IJ31, IJ32, othermechanism. The Residual bend IJ33, IJ34, IJ35, bend actuator convertsresulting from high IJ36, IJ37, IJ38, a high force low traveltemperature or high IJ39, IJ42, IJ43, actuator mechanism to stressduring IJ44 high travel, lower formation force mechanism. Transient Atrilayer bend Very good High stresses are IJ40, IJ41 bend actuator wherethe two temperature stability involved actuator outside layers are Highspeed, as a Care must be identical. This cancels new drop can be takenthat the bend due to ambient fired before heat materials do nottemperature and dissipates delaminate residual stress. The Cancelsresidual actuator only responds stress of formation to transient heatingof one side or the other. Reverse The actuator loads a Better couplingFabrication IJ05, IJ11 spring spring. When the to the ink complexityactuator is turned off, High stress in the the spring releases. springThis can reverse the force/distance curve of the actuator to make itcompatible with the force/time requirements of the drop ejection.Actuator A series of thin Increased travel Increased Some stackactuators are stacked. Reduced drive fabrication piezoelectric ink jetsThis can be voltage complexity IJ04 appropriate where Increasedactuators require high possibility of short electric field strength,circuits due to such as electrostatic pinholes and piezoelectricactuators. Multiple Multiple smaller Increases the Actuator forces IJ12,IJ13, IJ18, actuators actuators are used force available from may notadd IJ20, IJ22, IJ28, simultaneously to an actuator linearly, reducingIJ42, IJ43 move the ink. Each Multiple efficiency actuator need provideactuators can be only a portion of the positioned to control forcerequired. ink flow accurately Linear A linear spring is used Matches lowRequires print IJ15 Spring to transform a motion travel actuator withhead area for the with small travel and higher travel spring high forceinto a requirements longer travel, lower Non-contact force motion.method of motion transformation Coiled A bend actuator is Increasestravel Generally IJ17, IJ21, IJ34, actuator coiled to provide Reduceschip restricted to planar IJ35 greater travel in a area implementationsreduced chip area. Planar due to extreme implementations are fabricationdifficulty relatively easy to in other orientations. fabricate. FlexureA bend actuator has a Simple means of Care must be IJ10, IJ19, IJ33 bendsmall region near the increasing travel of taken not to exceed actuatorfixture point, which a bend actuator the elastic limit in flexes muchmore the flexure area readily than the Stress remainder of thedistribution is very actuator. The actuator uneven flexing iseffectively Difficult to converted from an accurately model even coilingto an with finite element angular bend, resulting analysis in greatertravel of the actuator tip. Catch The actuator controls a Very lowComplex IJ10 small catch. The catch actuator energy construction eitherenables or Very small Requires external disables movement of actuatorsize force an ink pusher that is Unsuitable for controlled in a bulkpigmented inks manner. Gears Gears can he used to Low force, low Movingparts are IJ13 increase travel at the travel actuators can requiredexpense of duration. be used Several actuator Circular gears, rack Canbe fabricated cycles are required and pinion, ratchets, using standardMore complex and other gearing surface MEMS drive electronics methodscan be used. processes Complex construction Friction, friction, and wearare possible Buckle plate A buckle plate can be Very fast Must staywithin S. Hirata et al, used to change a slow movement elastic limits ofthe “An Ink-jet Head actuator into a fast achievable materials for longUsing Diaphragm motion. It can also device life Microactuator”, converta high force, High stresses Proc. IEEE MEMS, low travel actuatorinvolved Feb. 1996, pp into a high travel, Generally high 418-423.medium force motion. power requirement IJ18, IJ27 Tapered A taperedmagnetic Linearizes the Complex IJ14 magnetic pole can increase magneticconstruction pole travel at the expense force/distance curve of force.Lever A lever and fulcrum is Matches low High stress IJ32, IJ36, IJ37used to transform a travel actuator with around the fulcrum motion withsmall higher travel travel and high force requirements into a motionwith Fulcrum area has longer travel and no linear movement, lower force.The lever and can be used for can also reverse the a fluid sealdirection of travel. Rotary The actuator is High mechanical Complex IJ28impeller connected to a rotary advantage construction impeller. A smallThe ratio of force Unsuitable for angular deflection of to travel of thepigmented inks the actuator results in actuator can be a rotation of thematched to the impeller vanes, which nozzle requirements push the inkagainst by varying the stationary vanes and number of impeller out ofthe nozzle. vanes Acoustic A refractive or No moving parts Large area1993 Hadimioglu lens diffractive (e.g. zone required et al, EUP 550,192plate) acoustic lens is Only relevant for 1993 Elrod et al, used toconcentrate acoustic ink jets EUP 572,220 sound waves. Sharp A sharppoint is used Simple Difficult to Tone-jet conductive to concentrate anconstruction fabricate using point electrostatic field. standard VLSIprocesses for a surface ejecting ink- jet Only relevant forelectrostatic ink jets

ACTUATOR MOTION Description Advantages Disadvantages Examples Volume Thevolume of the Simple High energy is Hewlett-Packard expansion actuatorchanges, construction in the typically required to Thermal Ink jetpushing the ink in all case of thermal ink achieve volume CanonBubblejet directions. jet expansion. This leads to thermal stress,cavitation, and kogation in thermal ink jet implementations Linear, Theactuator moves in Efficient High fabrication IJ01, IJ02, IJ04, normal toa direction normal to coupling to ink complexity may be IJ07, IJ11, IJ14chip surface the print head surface. drops ejected required to achieveThe nozzle is typically normal to the perpendicular in the line ofsurface motion movement. Parallel to The actuator moves Suitable forFabrication IJ12, IJ13, IJ15, chip surface parallel to the print planarfabrication complexity IJ33,, IJ34, IJ35, head surface. Drop FrictionIJ36 ejection may still be Stiction normal to the surface. Membrane Anactuator with a The effective Fabrication 1982 Howkins push high forcebut small area of the actuator complexity U.S. Pat. No. area is used topush a becomes the Actuator size 4,459,601 stiff membrane that ismembrane area Difficulty of in contact with the ink. integration in aVLSI process Rotary The actuator causes Rotary levers Device IJ05, IJ08,IJ13, the rotation of some may be used to complexity IJ28 element, sucha grill or increase travel May have impeller Small chip area friction ata pivot requirements point Bend The actuator bends A very small Requiresthe 1970 Kyser et al U.S. when energized. This change in actuator to bemade Pat. No. 3,946,398 may be due to dimensions can be from at leasttwo 1973 Stemme U.S. differential thermal converted to a large distinctlayers, or to Pat. No. 3,747,120 expansion, motion. have a thermal IJ03,IJ09, IJ10, piezoelectric difference across the IJ19, IJ23, IJ24,expansion, actuator IJ25, IJ29, IJ30, magnetostriction, or IJ31, IJ33,IJ34, other form of relative IJ35 dimensional change. Swivel Theactuator swivels Allows operation Inefficient IJ06 around a centralpivot. where the net linear coupling to the ink This motion is suitableforce on the paddle motion where there are is zero opposite forces Smallchip area applied to opposite requirements sides of the paddle, e.g.Lorenz force. Straighten The actuator is Can be used with Requirescareful IJ26, IJ32 normally bent, and shape memory balance of stressesstraightens when alloys where the to ensure that the energized. austenicphase is quiescent bend is planar accurate Double The actuator bends inOne actuator can Difficult to make IJ36, IJ37, IJ38 bend one directionwhen be used to power the drops ejected by one element is two nozzles.both bend directions energized, and bends Reduced chip identical. theother way when size. A small another element is Not sensitive toefficiency loss energized. ambient temperature compared to equivalentsingle bend actuators. Shear Energizing the Can increase the Not readily1985 Fishbeck actuator causes a shear effective travel of applicable toother U.S. Pat. No. motion in the actuator piezoelectric actuator4,584,590 material. actuators mechanisms Radial con- The actuatorsqueezes Relatively easy High force 1970 Zoltan U.S. Pat. striction anink reservoir, to fabricate single required No. 3,683,212 forcing inkfrom a nozzles from glass Inefficient constricted nozzle. tubing asDifficult to macroscopic integrate with VLSI structures processesCoil/uncoil A coiled actuator Easy to fabricate Difficult to IJ17, IJ21,IJ34, uncoils or coils more as a planar VLSI fabricate for non- IJ35tightly. The motion of process planar devices the free end of the Smallarea Poor out-of-plane actuator ejects the ink. required, thereforestiffness low cost Bow The actuator bows (or Can increase the Maximumtravel IJ16, IJ18, IJ27 buckles) in the middle speed of travel isconstrained when energized. Mechanically High force rigid requiredPush-Pull Two actuators control The structure is Not readily IJ18 ashutter. One actuator pinned at both ends, suitable for ink jets pullsthe shutter, and so has a high out-of- which directly push the otherpushes it. plane rigidity the ink Curl A set of actuators curl Goodfluid flow Design IJ20, IJ42 inwards inwards to reduce the to the regionbehind complexity volume of ink that the actuator they enclose.increases efficiency Curl A set of actuators curl Relatively simpleRelatively large IJ43 outwards outwards, pressurizing construction chiparea ink in a chamber surrounding the actuators, and expelling ink froma nozzle in the chamber. Iris Multiple vanes enclose High efficiencyHigh fabrication IJ22 a volume of ink. These Small chip area complexitysimultaneously rotate, Not suitable for reducing the volume pigmentedinks between the vanes. Acoustic The actuator vibrates The actuator canLarge area 1993 Hadimioglu vibration at a high frequency. be physicallydistant required for et al, EUP 550,192 from the ink efficient operation1993 Elrod et al, at useful frequencies EUP 572,220 Acoustic couplingand crosstalk Complex drive circuitry Poor control of drop volume andposition None In various ink jet No moving parts Various otherSilverbrook, EP designs the actuator tradeoffs are 0771 658 A2 and doesnot move. required to related patent eliminate moving applications partsTone-jet

NOZZLE REFILL METHOD Description Advantages Disadvantages ExamplesSurface This is the normal way Fabrication Low speed Thermal ink jettension that ink jets are simplicity Surface tension Piezoelectric inkrefilled. After the Operational force relatively jet actuator isenergized, simplicity small compared to IJ01-IJ07, it typically returnsactuator force IJ10-IJ14, IJ16, IJ20, rapidly to its normal Long refilltime IJ22-IJ45 position. This rapid usually dominates return sucks inair the total repetition through the nozzle rate opening. The inksurface tension at the nozzle then exerts a small force restoring themeniscus to a minimum area. This force refills the nozzle. Shuttered Inkto the nozzle High speed Requires IJ08, IJ13, IJ15, oscillating chamberis provided at Low actuator common ink IJ17, IJ18, IJ19, ink pressure apressure that energy, as the pressure oscillator IJ21 oscillates attwice the actuator need only May not be drop ejection open or close thesuitable for frequency. When a shutter, instead of pigmented inks dropis to be ejected, ejecting the ink drop the shutter is opened for 3 halfcycles: drop ejection, actuator return, and refill. The shutter is thenclosed to prevent the nozzle chamber emptying during the next negativepressure cycle. Refill After the main High speed, as Requires two IJ09actuator actuator has ejected a the nozzle is independent drop a second(refill) actively refilled actuators per nozzle actuator is energized.The refill actuator pushes ink into the nozzle chamber. The refillactuator returns slowly, to prevent its return from emptying the chamberagain. Positive ink The ink is held a slight High refill rate, Surfacespill Silverbrook, EP pressure positive pressure. therefore a high mustbe prevented 0771 658 A2 and After the ink drop is drop repetition rateHighly related patent ejected, the nozzle is possible hydrophobic printapplications chamber fills quickly head suffaces are Alternative for:,as surface tension and required IJ01-IJ07, IJ10-IJ14, ink pressure bothIJ16, IJ20, IJ22-IJ45 operate to refill the nozzle.

METHOD OF RESTRICTING BACK-FLOW THROUGH INLET Description AdvantagesDisadvantages Examples Long inlet The ink inlet channel Designsimplicity Restricts refill Thermal ink jet channel to the nozzlechamber Operational rate Piezoelectric ink is made long and simplicityMay result in a jet relatively narrow, Reduces relatively large chipIJ42, IJ43 relying on viscous crosstalk area drag to reduce inlet Onlypartially back-flow. effective Positive ink The ink is under a Dropselection Requires a Silverbrook, EP pressure positive pressure, so andseparation method (such as a 0771 658 A2 and that in the quiescentforces can be nozzle rim or related patent state some of the ink reducedeffective applications drop already protrudes Fast refill timehydrophobizing, or Possible from the nozzle. both) to prevent operationof the This reduces the flooding of the following: IJ01 pressure in thenozzle ejection surface of IJ07, IJ09-IJ12, chamber which is the printhead. IJ14, IJ16, IJ20, required to eject a IJ22,, IJ23-IJ34, certainvolume of ink. IJ36-IJ41, IJ44 The reduction in chamber pressure resultsin a reduction in ink pushed out through the inlet. Baffle One or morebaffles The refill rate is Design HP Thermal Ink are placed in the inletnot as restricted as complexity Jet ink flow. When the the long inletMay increase Tektronix actuator is energized, method. fabricationpiezoelectric ink jet the rapid ink Reduces complexity (e.g. movementcreates crosstalk Tektronix hot melt eddies which restrict Piezoelectricprint the flow through the heads). inlet. The slower refill process isunrestricted, and does not result in eddies. Flexible flap In thismethod recently Significantly Not applicable to Canon restrictsdisclosed by Canon, reduces back-flow most ink jet inlet the expandingactuator for edge-shooter configurations (bubble) pushes on a thermalink jet Increased flexible flap that devices fabrication restricts theinlet. complexity Inelastic deformation of polymer flap results in creepover extended use Inlet filter A filter is located Additional Restrictsrefill IJ04, IJ12, IJ24, between the ink inlet advantage of ink rateIJ27, IJ29, IJ30 and the nozzle filtration May result in chamber. Thefilter Ink filter may be complex has a multitude of fabricated with noconstruction small holes or slots, additional process restricting inkflow. steps The filter also removes particles which may block thenozzle. Small inlet The ink inlet channel Design simplicity Restrictsrefill IJ02, IJ37, IJ44 compared to the nozzle chamber rate to nozzlehas a substantially May result in a smaller cross section relativelylarge chip than that of the nozzle. area resulting in easier ink Onlypartially egress out of the effective nozzle than out of the inlet.Inlet shutter A secondary actuator Increases speed Requires separateIJ09 controls the position of of the ink-jet print refill actuator and ashutter, closing off head operation drive circuit the ink inlet when themain actuator is energized. The inlet is The method avoids the Back-flowRequires careful IJ01, IJ03, IJ05, located problem of inlet back-problem is design to minimize IJ06, IJ07, IJ10, behind the flow byarranging the eliminated the negative IJ11, IJ14, IJ16, ink-pushingink-pushing surface of pressure behind the IJ22, IJ23, IJ25, surface theactuator between paddle IJ28, IJ31, IJ32, the inlet and the IJ33, IJ34,IJ35, nozzle. IJ36, IJ39, IJ40, IJ41 Part of the The actuator and aSignificant Small increase in IJ07, IJ20, IJ26, actuator wall of the inkreductions in back- fabrication IJ38 moves to chamber are arranged flowcan be complexity shut off the so that the motion of achieved inlet theactuator closes off Compact designs the inlet. possible Nozzle In someconfigurations Ink back-flow None related to Silverbrook, EP actuator ofink jet, there is no problem is ink back-flow on 0771 658 A2 and doesnot expansion or eliminated actuation related patent result in inkmovement of an applications back-flow actuator which may Valve-jet causeink back-flow Tone-jet through the inlet.

NOZZLE CLEARING METHOD Description Advantages Disadvantages ExamplesNormal All of the nozzles are No added May not be Most ink jet nozzlefiring fired periodically, complexity on the sufficient to systemsbefore the ink has a print head displace dried ink IJ01, IJ02, IJ03,chance to dry. When IJ04, IJ05, IJ06, not in use the nozzles IJ07, IJ09,IJ10, are sealed (capped) IJ11, IJ12, IJ14, against air. IJ16, IJ20,IJ22, The nozzle firing is IJ23, IJ24, IJ25, usually performed IJ26,IJ27, IJ28, during a special IJ29, IJ30, IJ31, clearing cycle, afterIJ32, IJ33, IJ34, first moving the print IJ36, IJ37, IJ38, head to acleaning IJ39, IJ40,, IJ41, station. IJ42, IJ43, IJ44,, IJ45 Extra Insystems which heat Can be highly Requires higher Silverbrook, EP powerto the ink, but do not boil effective if the drive voltage for 0771 658A2 and ink heater it under normal heater is adjacent to clearing relatedpatent situations, nozzle the nozzle May require applications clearingcan be larger drive achieved by over- transistors powering the heaterand boiling ink at the nozzle. Rapid The actuator is fired in Does notrequire Effectiveness May be used success-ion rapid succession. In extradrive circuits depends with: IJ01, IJ02, of actuator someconfigurations, on the print head substantially upon IJ03, IJ04, IJ05,pulses this may cause heat Can be readily the configuration of IJ06,IJ07, IJ09, build-up at the nozzle controlled and the ink jet nozzleIJ10, IJ11, IJ14, which boils the ink, initiated by digital IJ16, IJ20,IJ22, clearing the nozzle. In logic IJ23, IJ24, IJ25, other situations,it may IJ27, IJ28, 1329, cause sufficient IJ30, IJ31, IJ32, vibrationsto dislodge IJ33, IJ34, IJ36, clogged nozzles. IJ37, IJ38, IJ39, IJ40,IJ41, IJ42, IJ43, IJ44, IJ45 Extra Where an actuator is A simple Notsuitable May be used power to not normally driven to solution wherewhere there is a with: IJ03, IJ09, ink pushing the limit of its motion,applicable hard limit to IJ16, IJ20, IJ23, actuator nozzle clearing maybe actuator movement IJ24, IJ25, IJ27, assisted by providing IJ29, IJ30,IJ31, an enhanced drive IJ32, IJ39, IJ40, signal to the actuator. IJ41,IJ42, IJ43, IJ44, IJ45 Acoustic An ultrasonic wave is A high nozzle HighIJ08, IJ13, IJ15, resonance applied to the ink clearing capabilityimplementation cost IJ17, IJ18, IJ19, chamber. This wave is can beachieved if system does not IJ21 of an appropriate May be alreadyinclude an amplitude and implemented at very acoustic actuator frequencyto cause low cost in systems sufficient force at the which alreadynozzle to clear include acoustic blockages. This is actuators easiest toachieve if the ultrasonic wave is at a resonant frequency of the inkcavity. Nozzle A microfabricated Can clear Accurate Silverbrook, EPclearing plate is pushed against severely clogged mechanical 0771 658 A2and plate the nozzles. The plate nozzles alignment is related patent hasa post for every required applications nozzle. A post moves Moving partsare through each nozzle, required displacing dried ink. There is risk ofdamage to the nozzles Accurate fabrication is required Ink The pressureof the ink May be effective Requires May be used pressure is temporarilywhere other pressure pump or with all IJ series ink pulse increased sothat ink methods cannot be other pressure jets streams from all of theused actuator nozzles. This may be Expensive used in conjunctionWasteful of ink with actuator energizing. Print head A flexible ‘blade’is Effective for Difficult to use if Many ink jet wiper wiped across theprint planar print head print head surface is systems head surface. Thesurfaces non-planar or very blade is usually Low cost fragile fabricatedfrom a Requires flexible polymer, e.g. mechanical parts rubber orsynthetic Blade can wear elastomer. out in high volume print systemsSeparate A separate heater is Can be effective Fabrication Can be usedwith ink boiling provided at the nozzle where other nozzle complexitymany IJ series ink heater although the normal clearing methods jets drope-ection cannot be used mechanism does not Can be require it. Theheaters implemented at no do not require additional cost in individualdrive some ink jet circuits, as many configurations nozzles can becleared simultaneously, and no imaging is required.

NOZZLE PLATE CONSTRUCTION Description Advantages Disadvantages ExamplesElectro- A nozzle plate is Fabrication High Hewlett Packard formedseparately fabricated simplicity temperatures and Thermal Ink jet nickelfrom electroformed pressures are nickel, and bonded to required to bondthe print head chip. nozzle plate Minimum thickness constraintsDifferential thermal expansion Laser Individual nozzle No masks Eachhole must Canon Bubblejet ablated or holes are ablated by an required beindividually 1988 Sercel et drilled intense UV laser in a Can be quitefast formed al., SPIE, Vol. 998 polymer nozzle plate, which is Somecontrol Special Excimer Beam typically a polymer over nozzle profileequipment required Applications, pp. such as polyimide or is possibleSlow where there 76-83 polysulphone Equipment are many thousands 1993Watanabe required is relatively of nozzles per print et al., U.S. Pat.No. low cost head 5,208,604 May produce thin burrs at exit holes SiliconA separate nozzle High accuracy is Two part K. Bean, IEEE micro- plateis attainable construction Transactions on machined micromachined fromHigh cost Electron Devices, single crystal silicon, Requires Vol. ED-25,No. 10, and bonded to the precision alignment 1978, pp 1185-1195 printhead wafer. Nozzles may be Xerox 1990 clogged by adhesive Hawkins etal., U.S. Pat. 4,899,181 Glass Fine glass capillaries No expensive Verysmall 1970 Zoltan U.S. Pat. capillaries are drawn from glass equipmentrequired nozzle sizes are No. 3,683,212 tubing. This method Simple tomake difficult to form has been used for single nozzles Not suited formaking individual mass production nozzles, but is difficult to use forbulk manufacturing of print heads with thousands of nozzles. Monolithic,The nozzle plate is High accuracy Requires Silverbrook, EP surfacedeposited as a layer (<1 μm) sacrificial layer 0771 658 A2 and micro-using standard VLSI Monolithic under the nozzle related patent machineddeposition techniques. Low cost plate to form the applications usingVLSI Nozzles are etched in Existing nozzle chamber IJ01, IJ02, IJ04,litho- the nozzle plate using processes can be Surface may be IJ11,IJ12, IJ17, graphic VLSI lithography and used fragile to the touch IJ18,IJ20, IJ22, processes etching. IJ24, IJ27, IJ28, IJ29, IJ30, IJ31, IJ32,IJ33, IJ34, IJ36, IJ37, IJ38, IJ39, IJ40, IJ41, IJ42, IJ43, IJ44Monolithic, The nozzle plate is a High accuracy Requires long IJ03,IJ05, IJ06, etched buried etch stop in the (<1 μm) etch times IJ07,IJ08, IJ09, through wafer. Nozzle Monolithic Requires a IJ10, IJ13,IJ14, substrate chambers are etched in Low cost support wafer IJ15,IJ16, IJ19, the front of the wafer, No differential IJ21, IJ23, IJ25,and the wafer is expansion IJ26 thinned from the back side. Nozzles arethen etched in the etch stop layer. No nozzle Various methods have Nonozzles to Difficult to Ricoh 1995 plate been tried to eliminate becomeclogged control drop Sekiya et al U.S. Pat. the nozzles entirely, toposition accurately No. 5,412,413 prevent nozzle Crosstalk 1993Hadimioglu clogging. These problems et al EUP 550,192 include thermalbubble 1993 Elrod et al mechanisms and EUP 572,220 acoustic lensmechanisms Trough Each drop ejector has Reduced Drop firing IJ35 atrough through manufacturing direction is sensitive which a paddlemoves. complexity to wicking. There is no nozzle Monolithic plate.Nozzle slit The elimination of No nozzles to Difficult to 1989 Saito etal instead of nozzle holes and become clogged control drop U.S. Pat. No.individual replacement by a slit position accurately 4,799,068 nozzlesencompassing many Crosstalk actuator positions problems reduces nozzleclogging, but increases crosstalk due to ink surface waves

DROP EJECTION DIRECTION Description Advantages Disadvantages ExamplesEdge Ink flow is along the Simple Nozzles limited Canon Bubblejet (‘edgesurface of the chip, construction to edge 1979 Endo et al GB shooter’)and ink drops are No silicon High resolution patent 2,007,162 ejectedfrom the chip etching required is difficult Xerox heater-in- edge. Goodheat Fast color pit 1990 Hawkins sinking via substrate printing requireset al U.S. Pat. No. Mechanically one print head per 4,899,181 strongcolor Tone-jet Ease of chip handing Surface Ink flow is along the Nobulk silicon Maximum ink Hewlett-Packard (‘roof surface of the chip,etching required flow is severely TIJ 1982 Vaught et shooter’) and inkdrops are Silicon can make restricted al U.S. Pat. No. ejected from thechip an effective heat 4,490,728 surface, normal to the sink IJ02, IJ11,IJ12, plane of the chip. Mechanical IJ20, IJ22 strength Through Ink flowis through the High ink flow Requires bulk Silverbrook, EP chip, chip,and ink drops are Suitable for silicon etching 0771 658 A2 and forwardejected from the front pagewidth print related patent (‘up surface ofthe chip. heads applications shooter’) High nozzle IJ04, IJ17, IJ18,packing density IJ24, IJ27-IJ45 therefore low manufacturing cost ThroughInk flow is through the High ink flow Requires wafer IJ01, IJ03, IJ05,chip, chip, and ink drops are Suitable for thinning IJ06, IJ07, IJ08,reverse ejected from the rear pagewidth print Requires special IJ09,IJ10, IJ13, (‘down surface of the chip. heads handling during IJ14,IJ15, IJ16, shooter’) High nozzle manufacture IJ19, IJ21, IJ23, packingdensity IJ25, IJ26 therefore low manufacturing cost Through Ink flow isthrough the Suitable for Pagewidth print Epson Stylus actuator actuator,which is not piezoelectric print heads require Tektronix hot fabricatedas part of heads several thousand melt piezoelectric the same substrateas connections to drive ink jets the drive transistors. circuits Cannotbe manufactured in standard CMOS fabs Complex assembly required

INK TYPE Description Advantages Disadvantages Examples Aqueous, Waterbased ink which Environmentally Slow drying Most existing ink dyetypically contains: friendly Corrosive jets water, dye, surfactant, Noodor Bleeds on paper All IJ series ink humectant, and May jets biocide.strikethrough Silverbrook, EP Modern ink dyes have Cockles paper 0771658 A2 and high water-fastness, related patent light fastnessapplications Aqueous, Water based ink which Environmentally Slow dryingIJ02, IJ04, IJ21, pigment typically contains: friendly Corrosive IJ26,IJ27, IJ30 water, pigment, No odor Pigment may Silverbrook, EPsurfactant, humectant, Reduced bleed clog nozzles 0771 658 A2 and andbiocide. Reduced wicking Pigment may related patent Pigments have anReduced clog actuator applications advantage in reduced strikethroughmechanisms Piezoelectric ink- bleed, wicking and Cockles paper jetsstrikethrough. Thermal ink jets (with significant restrictions) MethylMEK is a highly Very fast drying Odorous All IJ series ink Ethylvolatile solvent used Prints on various Flammable jets Ketone forindustrial printing substrates such as (MEK) on difficult surfacesmetals and plastics such as aluminum cans. Alcohol Alcohol based inksFast drying Slight odor All IJ series ink (ethanol, 2- can be used wherethe Operates at sub- Flammable jets butanol, printer must operate atfreezing and others) temperatures below temperatures the freezing pointof Reduced paper water. An example of cockle this is in-camera Low costconsumer photographic printing. Phase The ink is solid at No dryingtime- High viscosity Tektronix hot change room temperature, and inkinstantly freezes Printed ink melt piezoelectric (hot melt) is melted inthe print on the print medium typically has a ink jets head beforejetting. Almost any print ‘waxy’ feel 1989 Nowak Hot melt inks aremedium can be used Printed pages U.S. Pat. No. usually wax based, Nopaper cockle may ‘block’ 4,820,346 with a melting point occurs Inktemperature All IJ series ink around 80° C.. After No wicking may beabove the jets jetting the ink freezes occurs curie point of almostinstantly upon No bleed occurs permanent magnets contacting the print Nostrikethrough Ink heaters medium or a transfer occurs consume powerroller. Long warm-up time Oil Oil based inks are High solubility Highviscosity: All IJ series ink extensively used in medium for some this isa significant jets offset printing. They dyes limitation for use in haveadvantages in Does not cockle ink jets, which improved paper usuallyrequire a characteristics on Does not wick low viscosity. Some paper(especially no through paper short chain and wicking or cockle).multi-branched oils Oil soluble dies and have a sufficiently pigmentsare required. low viscosity. Slow drying Micro- A microemulsion is aStops ink bleed Viscosity higher All IJ series ink emulsion stable, selfforming High dye than water jets emulsion of oil, water, solubility Costis slightly and surfactant. The Water, oil, and higher than watercharacteristic drop size amphiphilic soluble based ink is less than 100nm, dies can be used High surfactant and is determined by Can stabilizeconcentration the preferred curvature pigment required (around of thesurfactant. suspensions 5%)

What is claimed is:
 1. An ink jet print head comprising: a nozzlechamber having an ink ejection port for ejection of ink from the nozzlechamber; an ink supply reservoir for supplying ink to said nozzlechamber; a plunger located within said nozzle chamber; and a linearstepper actuator interconnected to said plunger and adapted to actuatesaid plunger so as to cause the ejection of ink from said ink ejectionport.
 2. An ink jet print head as claimed in claim 1 wherein saidplunger has a hydrophobic surface located alongside at least one wall ofsaid nozzle chamber.
 3. An ink jet print head as claimed in claim 1wherein said linear actuator is driven in three phases by a series ofelectromagnets.
 4. An ink jet print head as claimed in claim 3 whereinsaid electromagnets are duplicated for each phase.
 5. An ink jet printhead as claimed in claim 4 wherein said each phase comprises fourelectromagnets.
 6. An ink jet print head as claimed in one of claims 3-5wherein said electromagnets are arranged in opposing pairs.
 7. An inkjet print head as claimed in claim 1 wherein said nozzle chamber has anopen wall along a back surface of said plunger.
 8. An ink jet print headas claimed in claim 1 wherein said nozzle chamber comprises a series ofposts adapted to form a filter to filter ink flowing into said nozzlechamber.
 9. An ink jet print head as claimed in claim 1 wherein saidlinear stepper actuator includes a guide at an end opposite said nozzlechamber for guiding the linear actuator.